During labor, it is sometimes necessary to monitor intrauterine pressure to more accurately assess contractions, and to aid in the detection of fetal distress so that appropriate remedial action can be taken. A condition that is frequently associated with fetal distress during labor is variable decelerations owing to a state of oligohydramnios, i.e., the presence of less than 300 milliliters amniotic fluid at term.
Loss of amniotic fluid is particularly of serious concern when it brings on a state of oligohydramnios during the intrapartum period of advanced labor with ruptured membranes. Amniotic fluid provides constant lubrication between the fetus, umbilical cord, and membranes. It also protects the fetus from external trauma and pressure by equalizing forces applied to the intrauterine contents.
Consequently, without adequate intrauterine fluid volume, fetal distress may occur. This distress may result from umbilical cord occlusion by entrapment between the fetus and the uterine wall, entanglement about the fetus, or from placental compression.
It is desirable, therefore, to maintain an adequate amniotic fluid volume in order to prevent these complications. Remedial action by intrauterine saline amnioinfusion therapy has been found useful for relieving fetal distress by replenishing intrauterine fluid volume to overcome the effects of oligohydramnios.
A discussion of amnioinfusion therapy can be found in Miyazaki et al., Amer. J. Obstet. Gynecol., 146, pages 670-678, 1983, (hereafter Miyazaki I); in Miyazaki et al., Amer. J. Obstet. Gynecol., 153, pages 301-306, 1985 (hereafter Miyazaki II); and in Gabbe et al., Amer. J. Obstet. Gynecol., 126, pages 353-355, 1976; and in Nageotte et al., Amer. J. Obstet. Gynecol., 153, pages 557-562, 1985.
A fluid filled intrauterine pressure catheter is typically used to effectively measure uterine contractions to avoid introducing air into the uterus and to measure the force of the intrauterine contractions transmitted through the uterine fluids and the liquid in the catheter to a pressure-measuring device, such as a strain gauge, a transducer, or the like.
In practicing amnioinfusion therapy, however, there is a need to simultaneously infuse fluids into the uterus and constantly monitor intrauterine pressure. As will be appreciated, this need particularly arises under emergency conditions, such as sudden severe prolonged decelerations.
In the past, attempts were made in Miyazaki I to infuse saline into the uterus by means of the fluid-filled pressure catheter by placing an extension tube leading to the saline in the line intermediate the transducer and the intrauterine catheter. However, this setup resulted in artificial pressure readings owing to resistance to outflow of the saline through the tip of the catheter, and a true reading could only be taken by shutting off the infusion flow.
As can be appreciated, under emergency conditions of sudden severe prolonged decelerations, it is necessary to rapidly infuse the uterus. Prior attempts with the setup described in Miyazaki II required connecting the intrauterine saline delivery tubing directly to the intrauterine pressure catheter, thereby foregoing the monitoring of the pressure altogether during saline delivery. Such a disability is a serious one, because the period of saline delivery is a period of flux, and it is especially necessary to monitor pressure during a period of flux.
There is a need, therefore, for an apparatus that allows for simultaneously monitoring intrauterine pressure during labor and delivering infusible fluid therein. To resolve the difficulty noted above, this invention relates to an apparatus that achieves the foregoing purpose.